The present invention relates generally to medical devices. More specifically, the present invention relates to catheters having improved flexibility control. In particular, the present invention includes angioplasty catheters having a slidable core wire disposed within and catheter shafts including a spine wire disposed within a polymeric tube.
Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating types of vascular disease. In particular, angioplasty is widely used for opening stenoses in the coronary arteries and is used for treating stenoses in other vascular regions.
One widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at the distal end and a guide wire lumen within at least a portion of the catheter shaft. Typically, a guide wire is inserted through the vascular system to a position near the stenoses, leaving a proximal portion of the guide wire extending from the patient. The proximal guide wire portion is threaded through the dilatation catheter guide wire lumen and the dilatation catheter advanced through the vascular system over the guide wire to the position near the stenoses. The treating physician manipulates the dilatation catheter until the balloon is positioned across the stenoses. The balloon is then inflated by supplying fluid under pressure through an inflation lumen in the catheter to the balloon. The inflation of the balloon widens the lumen through the stenosed area by pressing the inflating balloon wall against the lesion inside wall.
Flexibility, torqueability, and pushability are important properties in catheter design. Flexibility relates to the ability of the catheter to track through tortuous vessels, particularly through smaller secondary and tertiary coronary vessels. Torqueability refers to the ability to transmit torque from the proximal end to the distal end of the catheter. Treating physicians often require the ability to rotate a curved distal catheter end by rotating the proximal catheter end extending from the patient""s body. Rotating the catheter distal end allows the distal tip to be pointed toward a vessel opening, such as a coronary artery ostium. Pushability relates to the ability to transmit lateral force along the catheter without buckling. Flexibility, torqueability, and pushability sometimes conflict as design goals, with one or more being of predominant importance for a given region of a catheter. For example, pushability may be of more importance in the proximal region of a catheter, which may be required to push the distal remainder of the catheter. For example, flexibility may be of more importance in the distal region, which may be required to track tortuous vessel paths having small inside diameters. It may be desirable for catheter flexibility, and other properties, to be varied along the catheter length. What would be desirable is a catheter having varied flexibility along its length. A catheter having flexibility varied with time would also be desirable.
The present invention includes catheters having improved flexibility control. Some embodiments of the invention have movable core wires slidably disposed within lumen within the catheter shaft. One group of catheters is angioplasty catheters having a core wire slidably disposed within an inflation lumen. One angioplasty catheter includes a pressure seal disposed about the portion of core wire extending proximally from the catheter. In use, one angioplasty catheter having the movable core wire and seal can have the core wire alternately advanced and retracted during different stages of catheter insertion and angioplasty. The core wire can be advanced to enhance stiffness when pushability in a given catheter region is desired, and retracted when flexibility in a given region is desired.
One group of catheters includes a shaft portion having a spine wire or stiffening element disposed within the lumen of a polymeric tube. The spine wire can be formed of metal and have alternating wide and narrow portions formed of wide and narrow segments. The wide segments can approach or preferably touch the inside wall of the outer polymeric tube. The wide segments can contribute to shaft stiffness by their length and by the inter-segment distance between segments. One shaft includes a spine wire having substantially constant inter-segment distance. Another shaft includes a spine wire having distally increasing inter-segment distances, contributing to distally increasing flexibility.
One group of catheters incorporating the present invention has a fluid pathway formed within the outer polymeric tube. Catheters in this group can have alternating narrow and wide segments, with apertures or openings formed around or through the wide segments. One group of wide segments have openings or apertures formed between portions of the segments and the outer tube wall. One group of segments has apertures formed through the segments. Openings through or around the wide segments allow fluid flow through or past the wide segments, which could otherwise block or greatly inhibit fluid flow.
Catheter shafts having openings through the wide segments can be used to deliver fluid. One such fluid delivery catheter is a dye delivery catheter used to deliver radiopaque contour media for angiography. Other catheters incorporating the present invention are angioplasty catheters, which can use the tubular shaft containing the spine wire as an inflation tube for delivery of balloon inflation fluid.